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Solving the biggest mysteries in vision research

George Wigmore, Senior Communications Officer in the School of Health Sciences, attended Professor Joshua Solomon's inaugural lecture to hear about his work in visual psychophysics, revealing the relationship between the limits of perception and why things look the way they do.

by George Wigmore

Providing the newly appointed professor with the opportunity to inform colleagues, inaugural lectures not only mark the ascendency to the level of professor, but in the words of Professor Stan Newman, Dean of the School of Health Sciences, also enable them to "come and really tell us what they do". 

Joining City in 2000 - and coming by way of New York University; Syracuse, New York; Moffett Field, California and UCL's Institute of Ophthalmology - Professor Solomon first became acquainted with psychophysics in 1987. Since then he has taken this psychological approach toward understanding some of the visual system's biggest mysteries.

Small circlesThe lecture began with an illustration of the simultaneous contrast illusion: two donut shaped rings on a grey background - one black and one white. Although each ring has the same shade of grey in the middle, our visual system exaggerates the differences between the adjacent intensities.

This exaggeration is thought to be a consequence of lateral inhibition between neurones sensitive to luminance.

When photoreceptor cells in the eye are struck by light, they convert light into signals that can stimulate downstream neurones. Lateral inhibition enables these neurones to reduce the activity of their neighbours, thereby preventing them from reaching their maximum response. 

Professor Solomon tested various hypotheses regarding the psychological function of this inhibition. He speculated that the exaggeration of contrast in our environment doesn't matter, as the variety of potentially disadvantageous illusions caused by this exaggeration are massively outweighed by the benefits derived from energy efficiency, which may have no direct link to sensation and perception.

By preventing neurons from reaching their maximum response, lateral inhibition saves energy in the form of calories, meaning that ultimately we need to eat less to fuel our bodies.

Following the conclusion of Professor Solomon's talk, Professor Newman perfectly summed up the prevailing sentiment following our psychophysical tour of simultaneous contrast, praising Professor Solomon's "capacity to think outside the particular domain of his work".

This was not only a fitting end to the lecture highlighting Professor Solomon's interdisciplinary approach to research, but also provided a perfect start to his new professorship following some fascinating insight into psychophysics and the challenges -some of which will require using methods from outside the field - that lie ahead.

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